Backyard Aquaponics
A place to discuss aquaponics

This project is in the vague early stages, because I'm still actively working on the demand feeder, but I always like to start thinking about the next thing so I at least have a sence of direction before it's required.

I'm looking to create some linear movement to do various things. I figure I'd start small and move on toward ridiculous.

My demand fish feeder has taught a lot, but I still want to learn so much more. I suspect my project will include ...

1. Open and close a vent in a grow house.
2. Create a heliostat to explore the potential of throwing some extra light down the side of the house where it looks like I may be forced (by the evil Mrs. Bullwinkle) to move my system.
3. Create a solar tracker to keep my solar panel pointed at the sun as much as it can, and generate enough power to run my little system from it.
4. create a solar tracker that will auto correct regardless of current position so I can pilot my little electric boat up 2500km of Murray river and back at walking pace, and not have to think about where the sun is.

That last one might take a while longer

So...

My stage 1. thoughts are these...

If I attach a threaded rod to a continuous rotation servo, I should be able to attach a simple hex nut to the grow house vent, and rotate the servo, the hex nut should move up and down the threaded rod, opening and closing the vent as required.

A few temperature sensors, and a PICAXE chip, and stage one should work.

Any thoughts?

As for stages 2, 3 and 4, I thought about forming an x cross-section extrusion, with a light dependant resistor in each inner corner of the x. If the extrusion is long enough to cast a shadow onto the LDR that are not facing the sun, it should be possible to adjust two of the devices in project 1. so as to keep the solar panel pointing at the sun.

I also thought I might be able to make it so that it constantly adjusted randomly by say one degree to see if that was any better. If it wasn't, it could adjust back two degrees in the other direction. If both devices did this every few seconds, the panel would be always evolving toward the optimal position without ever having to actually know what that position is.

But I'm not sure that I'll need that last paragraph.



Any thoughts?



SuperVeg's "rack and pinion" words have proved to be a most interesting search. Google knows all about them.

nebbian just made my day by suggesting a car aerial.

power on vent opens. power off, vent closes.

Too cool, and $20

I'm confused... just how much logic is involved... in linear movement....

Its all about the pace.

Ahh... so you're talking logic controlled variable speed....

Sounds like a car window actuator would do the job....

Really that's a thing?

I always figured my windows in my car had the same mechanism as my old ford, but with a motor instead of the window winder handle thinggy.

I guess the difference is my old ford(s) had me exploring the inside of the door twice a year to replace door handles. After ten years and two fords, the guys at the parts shop would already have the door handles on the counter by the time I finished parking.

There are quit a few things described as linear actuators.

Lots are a long cylinder, with a short cylinder mounted near the base.

I suspect the short is the motor, and the long is something like my threaded rod with a hex nut. And the connection is a gearbox.

There are quite a few if you scroll down through this list...

http://www.alibaba.com/showroom/electri ... uator.html

Does anyone know how these things work? Is it just a threaded rod?

For the most yes, if you go scrounging for old medical equipment ie things to lift people out of wheelchairs etc you will be able to get some really good ones. I use one for a crane in my garage.

Edit
Some only power one way, for example the one above,its a safety feature to stop nurses crushing patients.

The domed greenhouse guy used linear actuators on his vents.

You can get some linear actuators from Surplus Center (on this side of the pond) fairly cheap, I haven't check shipping though. The good thing about LAs it they are generally slow so you can time things easily (ie. run 20 seconds to open vent 50%, etc.).

To determine best position for solar, could you use 2 detectors and point them at (say) 45º to each other - whichever gets the stronger signal causes movement towards it until the two signals balance?

Have a look at 3D printing for linear actuators. And for other groovy things to put the mind at rest (or is that open up the mind to new possibilities!)

That's pretty much what I had in mind, but with three or four sensors so I can track side to side and up and down.

I'm not sure how that would go if a shadow crossed the panel, or in cloud. That's why I was thinking about making random adjustments and retesting.

I could probably use a real time clock, and find the data for where the sun will be at any time and day, but that wont work on the electric boat without a compass chip, and I'm not sure how accurate they are.

There again you could just forget the electrical side of it and use those greenhouse vent openers that use expanding material to push and pull a ram